Syngas generator for blast furnace

ABSTRACT

A method for producing a syngas stream for use in a blast furnace, including providing a hot air stream to an ion transport membrane, thereby producing a hot nitrogen rich stream and a hot oxygen rich stream, providing a methane stream to the ion transport membrane, wherein the methane reacts with the hot oxygen rich stream thereby producing a syngas containing stream, introducing the syngas containing stream into a CO2 removal unit, thereby producing a carbon dioxide rich stream, and a hydrogen rich stream, and introducing the hydrogen rich stream into a blast furnace, thereby replacing at least a portion of the natural gas fuel required therein.

BACKGROUND

The blast furnace is a tall shaft-type furnace with a vertical stacksuperimposed over a crucible-like hearth. Iron-bearing materials (ironore, sinter, pellets, mill scale, steelmaking slag, scrap, etc.), cokeand flux (limestone and dolomite) are charged into the top of the shaft.A blast of heated air and also, in most instances, a gaseous, liquid orpowdered fuel are introduced through openings at the bottom of the shaftjust above the hearth crucible. The heated air burns the injected fueland much of the coke charged in from the top to produce the heatrequired by the process and to provide reducing gas that removes oxygenfrom the ore. The reduced iron melts and runs down to the bottom of thehearth. The flux combines with the impurities in the ore to produce aslag which also melts and accumulates on top of the liquid iron in thehearth. The iron and slag are drained out of the furnace throughtapholes.

The top pressure that is controlled by the top gas handling equipmentcan be as high as (40-50 psig) for very large furnaces, and the blastair has been enriched with oxygen as high as 40% total oxygen in theblast. Pressure at the inlet of the tuyeres depends on the controlledtop pressure and the quality of the raw materials, but can be as high as60 psig for a very large blast furnace. Oxygen enrichment reduces theamount of air needed per tonne of iron and therefore, the resultingquantities of BF Top Gas are reduced.

Ion transport membranes (ITMs) consist of ionic and mixed-conductingceramic oxides that conduct oxygen ions at elevated temperatures of1475-1650 F. Air is compressed, heated to 1650 F, and fed to ITM. Hotoxygen permeates through the membranes. The permeate pressure has to bekept low to provide oxygen partial pressure driving force across themembrane. Typically, 50% to 80% oxygen recovery seems possible.

SUMMARY

A method for producing a syngas stream for use in a blast furnace,including providing a hot air stream to an ion transport membrane,thereby producing a hot nitrogen rich stream and a hot oxygen richstream, providing a methane stream to the ion transport membrane,wherein the methane reacts with the hot oxygen rich stream therebyproducing a syngas containing stream, introducing the syngas containingstream into a CO2 removal unit, thereby producing a carbon dioxide richstream, and a hydrogen rich stream, and introducing the hydrogen richstream into a blast furnace, thereby replacing at least a portion of thefuel required therein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of one embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. While theinvention is susceptible to various modifications and alternative forms,specific embodiments thereof have been shown by way of example in thedrawings and are herein described in detail. It should be understood,however, that the description herein of specific embodiments is notintended to limit the invention to the particular forms disclosed, buton the contrary, the intention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of theinvention as defined by the appended claims.

It will of course be appreciated that in the development of any suchactual embodiment, numerous implementation-specific decisions must bemade to achieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

In typical operation, coal, natural gas and steam are added to the blastfurnace along with hot blast air. CH4 burns in the tuyeres to make H2Oand CO2 (CH4+2O2→CO2+2H2O) which then get reformed into H2 and CO (byreaction with hot coke, C+CO2→2CO, C+H2O→CO+H2) at high temperature(typically about 2000-2300° C.) found in the bottom of the blastfurnace. Additional steam also reacts with carbon in the coke to produceCO and H2. Part of H2 and CO reacts with iron ore in the upper shaft ofthe furnace, establishing a chemical equilibrium. Excess H2 and CO arefound in the top gas. Replacing H2 for natural gas and part of steamwill reduce the carbon requirement of the blast furnace. It will reducethe carbon requirement of the blast furnace thereby reducing the amountof CO and CO2 in the top gas, further improving the thermal efficiencyof blast furnace.

Ion Transport Membranes (ITM's) produce pure O2 from the hot air atabout 750-1000C. ITM Reactor has steam reforming catalyst such as Nideposited on the permeate side of the ITM membranes. If natural gas(CH4) and steam mixture is injected on the permeate side of ITM reactor,H2/CO rich syngas is produced. The syngas can be shifted to CO2 and H2.The shifted syngas is processed in a CO2 removal unit to produce pure H2and CO2 rich tail gas.

As shown in FIG. 1, the ITM syngas reactor is integrated into a blastfurnace design. The air pressure required for an ITM is typically lessthan 2 bara, and can be drawn from the first stage of the blast furnaceair compressor. The air is heated with oxygen-depleted effluent from theITM which has been combusted and expanded in a gas turbine for powerrecovery. There may be other ways to preheat the air such as x-exchangewith part of hot blast air from the stove. The natural gas and steammixture is injected into ITM reactor at the desired pressure of syngas,which may be in the range of 10-15 bar. The syngas from the ITM reactoris cooled and mixed with steam, sent to water gas shift reactor. Theheat in the shifted gas can be used to generate steam. The shifted gasis further cooled and processed in a CO2 removal unit to produce H2 richstream which is fed to the blast furnace. The H2 rich stream containsunconverted CO and CH4 The CO2 removal unit may be an amine wash unit,or any other system known to one skilled in the art.

A part of top gas can be compressed and mixed with syngas to the shiftreactor. This will recycle H2 and CO present in the top gas, whilecapturing more CO2.

Turning to FIG. 1, a syngas generator for a blast furnace is provided.An air stream 101 is compressed in compressor 102, thus creating acompressed, air stream 103. The compressed, air stream 103 is dividedinto a blast furnace air stream 104 and an ITM air stream 105.Compressed air stream 103 may have a pressure of about 25-35 psia. Blastfurnace air stream 104 may be further compressed in compressor 109. Theblast furnace air stream 104 is introduced into blast furnace stove 105,wherein it is heated, thereby producing heated blast furnace air stream106. Blast furnace stove 105 is heated by the combustion of at least aportion of blast furnace top gas stream 107. First combustion productstream 108 is then exhausted from the stove. Heated blast furnace airstream 106 may have a temperature of between 1800 and 2200 F.

ITM air stream 105, is introduced into a heat exchanger 112, wherein itexchanges heat with reduced pressure combustion stream 118, therebyproducing cooled combustion stream 121 and heated ITM air stream 113.

Heated ITM air stream 113 is introduced to an ion transfer membranereactor 114, Heated ITM air stream 122 may have a temperature of about1400 to 1830 F. Methane and steam mixture stream 135 is introduced intothe permeate side of the ITM reactor 114 at desired pressure of about50-150 psia. The stream 135 may be preheated (not shown). The ITMreactor produces a syngas stream 115 and a N2 rich retentate stream 116.The retentate stream 116 is then introduced into combustion unit 117,thereby producing combustion stream 118. Stream 134 reacts with O2permeating in ITM , generating syngas stream 115 containing H2, CO, andCO2.

The syngas stream 115 is introduced into water gas shift reactor 123therein producing shifted syngas stream 124. Shifted permeate stream 124is then introduced into steam generator 125 along with feed water stream126, thereby producing steam stream 128, and cooled shifted permeatestream 127. Cooled shifted permeate stream 127 may be introduced intoCO2 removal unit 129, thereby producing CO2 rich stream 130 and hydrogenstream 131. The hydrogen stream 131 may contain unconverted CO and CH4,and residual CO2. Hydrogen stream 131 may then be introduced into blastfurnace 132, to be used as reductant to process iron ore, and coke 133.Coal is typically injected in the bottom part of the blast furnace,through the tuyeres. Hydrogen stream 131 may be preheated to atemperature of at least 900 C (1667 F) before being injected into blastfurnace 132. Stream 131 may be heat exchanged(not shown) with other hotstreams such as stream 116 or a supplemental heater (not shown) may beused to further heat syngas stream 131 if necessary.

What is claimed is:
 1. A method for producing a hydrogen rich stream foruse in a blast furnace, comprising; a. providing a hot air stream to anion transport membrane, thereby producing a hot nitrogen rich stream anda hot oxygen rich stream, b. providing a methane and steam mixturestream to the ion transport membrane on the permeate side, wherein themethane reacts with the hot oxygen rich stream over a catalyst therebyproducing a syngas stream, c. introducing the syngas containing streaminto a CO2 removal unit, thereby producing a carbon dioxide rich stream,and a hydrogen rich stream, and d. introducing the hydrogen rich streaminto a blast furnace, thereby replacing at least a portion of the cokeand/or injected fuel required therein.
 2. The method of claim 1, whereinsaid hot air stream has a temperature greater than 750C.
 3. The methodof claim 2, wherein said hot air stream has a temperature between 750Cand 1000 C.
 4. The method of claim 1, further comprising introducing thesyngas containing stream into a heat recovery steam generator prior tointroduction into the CO2 removal unit, thereby producing steam.
 5. Themethod of claim 1, further comprising introducing the syngas containingstream into a water-gas shift reaction prior to introduction into theCO2 removal unit.
 6. The method of claim 1, wherein the hydrogen richstream displaces a significant portion of the fuel required in the blastfurnace.
 7. The method of claim 1, wherein the hot nitrogen rich streamprovides at least a portion of the heat required to produce the hot airstream.
 8. The method of claim 1, wherein at least a portion of the hotair stream is provided by a blast furnace air compressor.
 9. The methodof claim 1, wherein a part of the top gas stream is compressed and mixedwith ITM syngas upstream of shift reactor, and thus part of the hydrogenand carbon monoxide present in the top gas stream is recovered andrecycled to the blast furnace.